A swash-plate type compressor is one widely used in recent times for a refrigerant-compressor in an air conditioner of automotive. In such a compressor, a plural number of pistons, slidably fitted in a proper number of bores disposed in the cylinder block, is reciprocated by a swash-plate which is secured to a rotary shaft with a slant of a certain angle and rotatable therewith, for compressing a gas for air-conditioning a vehicle.
In a swash-plate type compressor the transmission of motive power from the swash-plate to the piston, for reciprocating the piston, is generally carried out through a shoe and a ball. As the material for the shoe (1) a casting of aluminum alloy including 20% silicon by weight, and small amount of manganese and copper, or (2) a hot or cold drawn copper alloy including 10% aluminum, 3.5% iron, by weight, and inevitable impurities up to 0.5%, by weight, has been conventionally employed. Either of the two is defective because of its low productivity, high material cost, and poor resistance to heavy-load and impact.
In order to eliminate these defects or shortcomings the inventors have invented a shoe made of a base material of steel (hereinafter simply called base material) and having a sintered powder copper alloy integrally formed on the sliding surface with the swash-plate, where sliding is particularly severe or outstanding. The fact is widely recognized that this shoe is highly resistant to heavy-load and impact as well as extremely superior in high-speed slidability, wear resistance, and seizure resistance at the sliding surface with the swash-plate under the condition of high-speed sliding. Later experiments have proved, however, that this shoe is still not one hundred percent satisfactory with respect to insufficient manifestation of those advantages on the sliding surface with the ball and the likelihood of abnormally rapid wearing of the sliding surface or seizure with the ball in case of low-speed operation which is liable to invite a lubrication shortage.